Herbicides are commonly formulated as wettable powders, dispersible granules, emulsifiable concentrates, aqueous flowables and the like. Of these, the dispersible granular formulations offer ease of handling, for instance spills can be readily swept up, and of course, the absence of an organic, flammable solvent. In general, such formulations offer increased chemical stability over liquid formulations. Further, granular formulations offer the ability to employ higher concentrations of active ingredient, i.e. 70% or greater vs. 15% to 45% for the average liquid formulation and, thereby, significantly reduce the bulk of the final product.
The most widely used method for preparing water dispersible granular compositions is pan granulation. However, the particle size of the final granulated product is difficult to control and can give the final product uneven and undesirable dispersibility properties. Pan granulation is also an inherently dusty process.
An alternative method to formulate a granular composition is by extrusion. Extruded dry granular compositions, however, tend to produce tightly compacted granules which possess poor dispersibility and suspendability.
Therefore, it is an object of this invention to provide a herbicidal extruded granular composition with no dust and improved water dispersibility and suspendability.
It is a further object of this invention to provide an herbicidal extruded granular composition having granules of substantially uniform size and density.
It is also an object of this invention to provide a herbicidal extruded granular composition requiring less surfactant than the corresponding pan granulated product.
It is a further object invention to provide a herbicidal extruded granular composition that is solvent-free and able to be packaged in a water soluble container, resulting in increased environmental compatibility and user safety.